/**
 * @param {ListNode} list1
 * @param {ListNode} list2
 * @return {ListNode}
 */
 var mergeTwoLists = function(l1, l2) {
    if (l1 === null) {
        return l2;
    } else if (l2 === null) {
        return l1;
    } else if (l1.val < l2.val) {
        
        l1.next = mergeTwoLists(l1.next, l2);
        console.log(l1)
        return l1;
    } else {
        l2.next = mergeTwoLists(l1, l2.next);
        console.log(l2, "2")
        return l2;
    }
};